The present invention relates to a method and apparatus for providing the wrappers of rod-shaped smokers' products with perforations or other types of holes which admit atmospheric air into the column of tobacco smoke entering a smoker's mouth. More, particularly, the invention relates to a method and apparatus for regulating and maintaining at a desired level the rate of admission of cool atmospheric air into the column of tobacco smoke in a region which is preferably close to one end of a rod-shaped smoker's product, such as a plain or filter tipped cigarette, cigarillo or cigar. Still more particularly, the invention relates to improvements in a method and apparatus for regulating the permeability of wrapping material for rod-shaped smokers' products to insure that the wrapper of each and every product which leaves the maker (or at least the great majority of such products) will exhibit an optimum permeability.
The provision of the wrappers of cigarettes or like rod-shaped smokers' products (hereinafter called cigarettes or filter cigarettes) with so-called climatic zones (i.e., with zones which are perforated in order to permit energy of cool atmospheric air) is becoming increasingly popular; in fact, many manufacturers of cigarettes demand that each machine for the making of cigarettes be equipped with apparatus which can perforate selected portions of the wrappers in a region close to one or both ends of a plain cigarette or in a region close to (and including) the mouthpiece of a filter cigarette. The admission of cool atmospheric air into the column of tobacco smoke flowing into the smoker's mouth reduces the percentage of nicotine and condensate. Furthermore, atmospheric air reduces the temperature of the smoke column. Presently known proposals to perforate the wrappers of cigarettes or the like are not entirely satisfactory, mainly because the quantity of admitted atmospheric air varies from cigarette to cigarette or from cigarettes in one pack or carton to cigarettes in another pack or carton. This is an irritant to the purchaser of cigarettes, especially if the differences between the permeabilities of wrappers of successively lighted cigarettes are readily detectable.